What does “art will be arched 12%” and how do I do it in Photoshop (or other)?

Question

I have some drinking mugs that can hold artwork in the liner. I have just the mugs, not any pre-printed art. The artwork template (here is the PDF) states

After submission of artwork, art will be arched 12 % for curvature.

I understand that is to compensate for the tapered shape of the mug - I assume this will change the art into a trapezoidal shape. What does the 12% mean? Is it the ratio of the width at the top and the bottom (i.e. the bottom is 88% the length of the top) or something else?

Using Photoshop or something similar (I have access to Photoshop and Corel Painter Essentials), how can this be accomplished?

Answer 1

Take the whole design, group it, then in the menu, Object - Envelope Distort - Make with Warp. Since the bottom part is smaller yes curve it. Secondly, Check it physically by making a cup from the print. (Old Graphic Design tricks).. And just like Scott just wrote. Ask the printer. They are your friend.

Answer 2

You shouldn't concern yourself. The production house is simply letting you know that they will be adjusting the art for final production.

If you are really unsure, you need to ask the author what is exactly meant by that line.